Type 2 Why the difference in readings minutes apart?

Today I did a fingerprick test. The first one didn't register immediately, nor did it error, but after applying a bit more blood it came back with a reading of 4.9. I thought that was too low, so did another test using a different finger and new strip immediately after, and it came back with 6.7. I thought this was too high, so I did another test using the same blood but a different strip, and it came back as 6.1.

I used a new strip for each test, and they don't expire until July 2025, and I always close the container after taking one out.

I was just wondering what the reasons for this could be.

It's just as well that the first one wasn't correct, as it was two hours after a sourdough sandwich. I'd have thought I was cured!